Hey Michael,
Thanks for writing. I think there’s a major difference between an attempt vs. the actual outcome. We certainly associate the gas chamber with mass extermination and the Holocaust, as we should. No way of putting another human being to death is actually “humane.” In 1923, however, the Nevada Supreme Court complimented the Nevada legislature for its implementation of the gas chamber as “the death penalty in the most humane manner known to modern science.”
http://newtolasvegas.com/2018/05/31/unique-execution-of-las-vegas-killer-would-not-be-nevadas-first/